A conventional method for coupling devices that operate at different speeds (or asynchronously from each other) is to use a first-in, first-out (FIFO) memory. To prevent an overflow condition (i.e., where incoming data is written over unread data), the distance between read and write pointers is monitored and data input stopped when the FIFO is almost full (i.e., the write pointer is within a predetermined threshold of the read pointer).
In a serial advanced technology attachment (Serial-ATA) application, a FIFO is used to receive different size information packets from another device. When the FIFO detects an almost full condition, a HOLD is sent to the transmitter. Upon receiving the HOLD, the transmitter stops sending the current information packet until told to begin again by the receiver.
Conventional Serial-ATA devices have receive FIFOs sized large enough so that non-data FIS type payloads can be written without nearing the overflow threshold. However, the large FIFOs require more silicon, thus increasing the cost of the devices.